Ether acids and ester derivatives thereof

ABSTRACT

3,3&#39;-(3-Methylpentylene-1,5-dioxy) dipropionic acid and esters thereof useful as plasticizers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to ether acids and esters thereof. Moreparticularly, the invention relates to3,3'-(3-methylpentylene-1,5-dioxy) dipropionic acid and esters thereofuseful as plasticizers.

2. Description of the Prior Art

Common glycols such as ethylene glycol, butylene glycol, and diethyleneglycol have been cyanoethylated by reaction with acrylonitrile and thensubjected to hydrolysis and alcoholysis to give the correspondingdiacids and diesters. See, for instance, Nazarov et al, J. Gen Chem.USSR (Engl. trans.) 24 (1954).

Various ether-diesters have been suggested as synthetic lubricants forapplications where ordinary mineral lubricating oils are not entirelysatisfactory. See, for instance, U.S. Pat. No. 2,886,590 showing thediester of isoamyl alcohol and 3,6,9-trioxa-1,11-undecanedioic acid.

SUMMARY OF THE INVENTION

In accordance with the present invention there are provided novel etheracids and esters thereof having the formula ##STR1## in which the Rgroups, which may be the same or different, are H or alkyl of 1 to 18carbon atoms each.

The 3,3'-(3-methylpentylene-1,5-dioxy) dipropionic acid and estersthereof derived from 3-methylpentane-1,5-diol in accordance with thepresent invention are not only unique in their symmetricalbranched-chain structure but are found to have unexpectedly superiorproperties compared to the ethylene glycol analogs known heretofore.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The 3-methylpentane-1,5-diol starting material for the ether acids andester derivatives of the present invention is available from severalsources. Conveniently, such materials are obtained by reaction ofisobutene and formaldehyde followed by the hydrogenation of theunsaturated diol thus obtained.

The cyanoethylation of 3-methylpentane-1,5-diol with acrylonitrile andhydrolysis and alcoholysis thereof to give the novel acids and estersthereof in accordance with the present invention is readilyaccomplished. Acrylonitrile is added to the 3-methylpentane-1,5-diol inthe presence of alkaline catalyst, for example an aqueous solution ofpotassium hydroxide, with vigorous stirring at temperatures of fromabout 20° to 30° C. The dicyanoethyl ether thus obtained is hydrolyzed,for example by the addition of aqueous hydrochloric acid at temperaturesof from about 90° to 100° C. Alcoholysis, for example with2-ethyl-1-hexanol, occurs readily by mixing the diacid and alcohol andheating at reflux temperatures for about one hour.

The reaction of 3-methylpentane-1,5-diol in the preparation of the novelether acids and esters as described above is conveniently illustrated bythe following schematic equation and structural formulas: ##STR2##

The esters of the ether acids in accordance with the invention areprepared by conventional esterification techniques with the desiredalcohols. The alcohols may be aliphatic or cycloaliphatic alcohols of 1to 18 carbon atoms. However, preferred alcohols are the straight-chainand branched-chain alkyl alcohols of from 4 to 12 carbon atoms, sincethe esters derived therefrom are particularly suited as plasticizers.

The following examples further illustrate the preparation of the novelether acids and esters of the invention. Unless otherwise indicated,percentages are on a weight basis.

EXAMPLE 1 Preparation of 3,3'-(3-Methylpentylene-1,5-dioxy) DipropionicAcid

In a 3-necked flask equipped with reflux condenser, water bath,thermometer, and mechanical stirrer a solution of 3.12 g. potassiumhydroxide in 3.46 g. of water was added to 111.6 g. of3-methylpentane-1,5-diol (0.94 mol). While the water bath maintained thetemperature at 22° to 28° C, acrylonitrile in the amount of 103.3 g(1.88 mols) was added dropwise with vigorous stirring. After about fourhours the NMR spectrum of the undiluted reaction mixture was consistentwith nearly complete conversion to the dicyanoethyl intermediate, peakareas corresponding to 2.9 methyl protons, 5.1 unshifted methylene andmethine protons, 3.9 alpha-cyano protons, 7.3 alpha-oxy protons, 0.2hydroxyl protons, and 0.5 vinyl protons being observed.

To the above dicyanoethyl intermediate was added 275.1 g. of 37.5%hydrochloric acid (103.1 g. HCl) amounting to 2.83 mols. The reactiontemperature was maintained at 90° to 100° C for 2 hours with stirring.The reaction mixture turned dark brown and ammonium chlorideprecipitated, following which the mixture was cooled and allowed tostand overnight. The ammonium chloride precipitate was filtered andwashed with ether. The filtrate was extracted twice with ether and theextract was combined with the ether washing from the ammonium chlorideprecipitate. The combined extract and ether wash was dried with calciumchloride and then with magnesium sulfate and the ether evaporated in arotary evaporator with the bath temperature gradually increasing to theboiling point of water to give 214 g. (94% of the theoretical) of3,3'-(3-methylpentylene-1,5-dioxy) dipropionic acid. The crude acid waspurified by extracting its ether solution with aqueous base, acidifying,extracting again with ether, and removing the ether first under reducedpressure and finally with a stream of nitrogen. The NMR spectrumconsisted of a singlet at 11.46 ppm (2 protons) assigned to the acidproton; triplets of 3.52 ppm (4 protons, J=6 c.p.s.) and 3.42 ppm (4protons, J=6 c.p.s.), each assigned to one of the pairs of methylenegroups next to oxygen; a triplet at 2.50 ppm (4 protons, J=6 c.p.s.)assigned to the methylene group next to carboxyl; a doublet at 0.88 ppm(3 protons, J=5 c.p.s.) assigned to the methyl group; and a broad peakwith fine structure centered at 1.5 ppm, assigned to the remainingmethylene and methine protons.

EXAMPLE 2 Preparation of Di(2-ethyl-1-hexyl) Ester of3,3'-(3-Methylpentylene-1,5-dioxy) Dipropionic Acid

In a reaction flask equipped for reflux and azeotropic removal of water,52.46 g. (0.20 mol) of the ether acid of Example 1, 53.39 g. of2-ethyl-1-hexanol (0.41 mol), 1.0 g. of sulfonic acid ion exchange resin(Dowex 50W-X8), 100 ml. of benzene, and 2 drops of concentrated sulfuricacid was stirred and heated under reflux for five hours. Approximately 7ml. of water (0.4 mol) was collected. The contents of the reaction flaskwere then cooled and washed with 20 ml. of 10% aqueous sodium hydroxide.An emulsion was formed and allowed to break overnight. The organic layerwas then washed with 20 ml. of water, dried with magnesium sulfate, andfiltered. Two drops of acetic acid were added and the benzene evaporatedunder reduced pressure. Finally the mixture was stripped at 100° C and40 mm/Hg. About 10 ml. of material distilled overhead at 35° to 40° C at0.1 to 0.3 mm/Hg. The stripped material had an NMR spectrumcorresponding to the di(2-ethyl-1-hexanol) ester.

EXAMPLE 3 Preparation of Dibutyl Ester of3,3'-(3-Methylpentylene-1,5-dioxy) Dipropionic Acid

Using the procedure of Example 2, 52.46 g. (0.2 mol) of the ether acidof Example 1 and 88.94 g. (1.2 mol) of 1-butanol were reacted and theproduct worked up to give material of NMR spectrum corresponding to thedibutyl ester of 3,3'-(3-methylpentylene-1,5-dioxy) dipropionic acid.

EXAMPLE 4 Preparation of Dihexyl Ester of3,3'-(3-Methylpentylene-1,5-dioxy) Dipropionic Acid

Using the procedure of Example 2, 52.46 g. (0.2 mol) of the ether acidof Example 1 and 49.05 g. (0.48 mol) of 1-hexyl alcohol were reacted andthe product worked up to give material of NMR spectrum corresponding tothe dihexyl ester of 3,3'-(3-methylpentylene-1,5-dioxy) dipropionicacid.

For the purposes of comparison a number of corresponding diesters of thedipropionic acid analogs derived from ethylene glycol were preparedusing the procedure of the foregoing examples of the invention.

The above diesters and comparative prior art esters were thenincorporated into polyvinyl chloride (PVC) by mixing 39 grams of PVC, 26grams of ester and 0.65 gram of a commercial barium/cadmium lauratestabilizer. Mixing was accomplished by working the mixture on a rubbermill for 10 minutes at 310° to 320° F. The resulting sheets were thenmolded (using a conventional PVC mold) into film sheets 4 inches × 4inches, in either 10-mil or 70-mil thicknesses. Molding temperature was330° F. These films were then tested by the methods described in"Plasticizers: Paraplex and Monoplex," Rohm and Hass Co., 1960, pp.84-89. The following tests were carried out:

1. Volatility -- The details of the test are given in the abovereference at page 84. In general, the weight loss of a PVC filmcontaining a plasticizer at 90° C for 24 hours is measured and reportedas percent weight loss.

2. Soapy Water Extraction -- The details of this test are in the abovepublication, pp. 85-86. In general, the weight loss of a plasticized PVCsample immersed in a 1% aqueous soap solution at 90° C for 24 hours ismeasured and reported as percent weight loss.

3. Hexane Extraction -- The details of the test method are given in theabove-cited reference, page 86. In general, the loss in weight of a PVCfilm containing a plasticizer is determined after 2 hours' immersion inn-hexane at 25° C.

4. Hardness -- A slightly modified Shore Durometer Hardness Test, asdescribed on page 87 of the reference, was utilized. In this test, theinitial value (0 sec.) of the hardness of a 70-mil sheet is determinedusing the Shore Durometer with a 2-pound (A) loading.

5. Flex (TF) Temperature -- This test was carried out by the well-knownmethod of Clash and Berg [Ind. & Eng. Chem. 34, 1218 (1942)]. In thistest, the angular twist of a rectangular test specimen is determined byapplying a controlled torque of 5.68 × 10³ dyne-cm to the sample 5seconds after exposure to various low test temperatures. The temperatureat which the angular twist is 200° of arc is then taken as the "flex"(TF) temperature. Flex temperature is defined as "the lower temperaturelimit of the compound's usefulness as an elastomer."

The results of the above tests on PVC-containing representative examplesof the esters of the present invention are given in the Table.

                                      TABLE                                       __________________________________________________________________________                    70 Mil                                                                             Low                                                                      Initial                                                                            Temp.                                                                              n-Hexane                                                                            Soapy Water                                   Run             Shore A                                                                            Torsion                                                                            Extraction                                                                          Extraction                                                                           Volatility                             No.                                                                               Plasticizer Hardness                                                                           Modulus                                                                            Wt. Loss                                                                            Wt. Loss                                                                             Wt. Loss                               __________________________________________________________________________    1  Dioctyl orthophthalate                                                                     80   -34° C                                                                      31%   12%     9%                                    2  Diisodecyl adipate                                                                         82   -54° C                                                                      39%    5%     7%                                    3  Di(2-ethylhexyl) ester                                                                     72   -55° C                                                                      22%   36%    22%                                       of ethylene glycol                                                            dipropionic adduct                                                         4  Di(2-ethylhexyl) ester                                                                     81   -54° C                                                                      33%   22%     5%                                       of 3,3'-(methyl-                                                              pentylene-1,5-dioxy)                                                          dipropionic acid                                                           5  Dihexyl ester of 3,3'-                                                                     79   -54° C                                                                      30%   32%     9%                                       (3-methylpentylene-1,5-                                                       dioxy) dipropionic acid                                                    6  Dihexyl ester of ethyl-                                                                    77   -56° C                                                                      21%   35%    15%                                       ene glycol dipropionic                                                        adduct                                                                     __________________________________________________________________________

The above test results show that the symmetrical3,3'-(3-methylpentylene-1,5-dioxy) propionic acid and esters thereof inaccordance with the present invention possess surprisingly superiorproperties which distinguish them from other materials known heretoforein the art.

While the character of this invention has been described in detail withillustrative examples, this has been done by way of illustration onlyand without limitation of the invention. It will be apparent to thoseskilled in the art that modifications and variations of the illustrativeexamples may be made in the practice of the invention within the scopeof the following claims.

I claim:
 1. Compounds having the formula ##EQU1## in which the R groups,which may be the same or different, are H or alkyl of 1 to 18 carbonatoms each.
 2. Compound of claim 1 in which R is H.
 3. Compounds ofclaim 1 in which the R groups are primary alkyl of from 4 to 12 carbonatoms.
 4. Compounds of claim 1 in which the R groups are 2-ethylhexyl.5. Compound of claim 1 in which the R groups are 1-hexyl.